Water softening is a significant concern for many businesses, including hospitals and hotels. Hard water creates problems for the equipment used in these facilities as well as other businesses that require a large supply of soft water. One effect of hard water is that soaps and detergents lose some of their effectiveness. Instead of dissolving completely, soap combines with the minerals to form a coagulated soap curd which can cause problems with film and laundry effectiveness. This can keep dirt trapped in the fibers, and it can stiffen and roughen the towels and sheets that hotels and hospitals need to wash every day.
The solution to the problem is to get rid of the minerals such as calcium and magnesium that is found in hard water. While there are chemical treatments that do this, the most popular answer is a water softener. Water softeners are typically use an ion exchange to remove the minerals from the water using a brine solution to effect the removal. The heart of a water softener is a mineral tank that is filled with small polystyrene beads, also known as resin or zeolite. The beads carry a negative charge. Calcium and magnesium in water both carry positive charges. Thus, these minerals will attach to the beads as the hard water passes through the mineral tank. The brine is saturated with Sodium ions, which also have a positive charge, albeit not as strong as the charge on the calcium and magnesium. When a very strong brine solution is flushed through a tank that has beads already saturated with calcium and magnesium, the sheer volume of the sodium ions is enough to drive the calcium and magnesium ions off the beads. Water softeners have a local brine tank that generates the brine necessary to conduct the water softening for businesses that use a lot of soft water.
In normal operation, hard water moves into the mineral tank and the calcium and magnesium ions move to the beads, replacing sodium ions. The sodium ions from the brine go into the water. Once the beads are saturated with calcium and magnesium, the unit enters a 3-phase regenerating cycle. First, the backwash phase reverses water flow to flush dirt out of the tank. In the recharge phase, the concentrated sodium-rich salt solution is carried from the brine tank through the mineral tank. The sodium collects on the beads, replacing the calcium and magnesium, which go down the drain. Once this phase is over, the mineral tank is flushed of excess brine and the brine tank is refilled.
Brine tanks are usually above ground, but where space is particularly critical underground brine making apparatus can be utilized. However, there are unique challenges to underground brine making systems, namely that it is challenging to ensure complete brine saturation for the entire brine solution. That is, unlike an above ground briner that allows for even salt distribution from a single field point, underground briners do not provide for even salt distribution throughout the horizontal vessel. Salt tends to collect below the point of deposit rather than spreading evenly along the tank bottom surface. When water enters the tank, areas of the lower surface near the ends may have little or no salt present, leading to water with minimal salt saturation. If the vessel does not have salt distributed throughout, this non-saturated water and not brine can enter the outlet collection plenum. The problem then is to ensure that salt and water are distributed evenly and thoroughly so that only brine exits the tank.